1. Field of the Invention
The present invention relates to a surface-mount type light emitting diode surface-mountable on a motherboard and a method of manufacturing it, and particularly to a surface-mount type light emitting diode of such a type wherein a wavelength for a light emitting diode element is converted into another to charge a luminescent color.
2. Description of the Related Art
As this type of wavelength-conversion type light emitting diode, there has been known one shown in FIG. 1 by way of example (see JP-A No. H7-99345). This is a lead-frame type light emitting diode 1, which is one having a structure wherein a concave portion 3 is defined in a metal post 2 on one side of a lead frame, a light emitting diode element 4 is fit on and fixedly secured to the concave portion 3, and the light emitting diode element 4 and a metal post 5 on the other side of the lead frame are connected to each other by a bonding wire 6, whereas a resinous material 7 mixed with a wavelength-converting luminescent material or the like is charged into the concave portion 3 and the entire body thereof is sealed with a shell-shaped transparent epoxy resin 8. Since the wavelength of light emitted from the light emitting diode element 4 is wavelength-converted by the resinous material 7 charged into the concave portion 3, the light emitting diode 1 comprising such a structure is capable of applying luminescent light having a luminescent color different from the original luminescent color of the light emitting diode element 4.
However, the light emitting diode 1 wherein the whole body referred to above is simply sealed with the transparent epoxy resin 8, has a problem in that since the wavelength-converting luminescent material or the like mixed into the resinous material 7 has the property of being easy to age due to externally-incoming ultraviolet rays or the like, the luminescent material is susceptible to the externally-incoming ultraviolet radiation.
A first object of the present invention is to form a structure of a light emitting diode as a surface-mount type and allow the wavelength-converting material such as the luminescent material to be insusceptible to externally-incoming ultraviolet radiation or the like to thereby control aging of the wavelength-converting material.
A second object of the present invention is to avoid a reduction in the brightness of the light emitting diode due to the structure insusceptible to the ultraviolet radiation.
According to one aspect of the invention, for achieving the object, there is provided a surface-mount type light emitting diode, comprising a light emitting diode element placed on an upper surface of a glass epoxy substrate and having electrodes, a pair of electrodes formed on the glass epoxy substrate, a resin encapsulator for sealing an upper portion of the glass epoxy substrate, the electrodes and the pair of electrodes being connected to one another, a reflection frame placed around the light emitting diode element, a first resin encapsulator mixed with a wavelength-converting material, the first resin encapsulator being charged into the reflection frame to seal the light emitting diode element, a second resin encapsulator, a third resin encapsulator used as a surface layer, and an ultraviolet absorbent mixed into at least the third resin encapsulator, and wherein the second resin encapsulator and the third resin encapsulator are superimposed over the glass epoxy substrate including the reflection frame in layer form to seal the entirety of the first resin encapsulator.
In a surface-mount type light emitting diode according to another aspect of the present invention, an upper surface of the first resin encapsulator is placed in a position below an upper edge of the reflection frame.
In a surface-mount type light emitting diode according to a further aspect of the present invention, the wavelength-converting material mixed into the first resin encapsulator is a luminescent material comprising a fluorescent dye or fluorescent pigment.
In a surface-mount type light emitting diode according to a still further aspect of the present invention, the second resin encapsulator is mixed with a diffusing agent for diffusing wavelength-converted light.
In a surface-mount type light emitting diode according to a still further aspect of the present invention, the third resin encapsulator covers the entirety of the second resin encapsulator and is shaped in the form of a cap whose outer peripheral portion is bonded and fixed to the upper surface of the glass epoxy substrate.
In a surface-mount type light emitting diode according to a still further aspect of the present invention, a condenser lens portion is formed on an upper surface of the third resin encapsulator.
In a surface-mount type light emitting diode according to a still further aspect of the present invention, the light emitting diode element is a blue light emitting element comprised of a gallium-nitride system compound semiconductor or a silicon-carbide system compound semiconductor.
There is also provided a method of manufacturing a surface-mount type light emitting diode, comprising the following steps: a step for bonding and fixing a reflection-frame assembler to an upper surface of a glass epoxy assembled substrate with a pair of electrodes formed thereon, a step for placing light emitting diode elements inside reflection frames respectively and connecting electrodes of the light emitting diode elements and respective pairs of electrodes formed on the glass epoxy assembled substrate respectively, a step for charging a first resin encapsulator mixed with a wavelength-converting material into each of the reflection frames to thereby seal each of the light emitting diode elements, a step for sealing an upper portion of the glass epoxy assembled substrate including each reflection frame with a second resin encapsulator mixed with a diffusing agent, a step for sealing an upper surface of the second resin encapsulator with a third resin encapsulator mixed with an ultraviolet absorbent, and a step for cutting the glass epoxy assembled substrate along cut lines supposed thereon every sizes of substrates constituting light emitting diodes to thereby divide it into each individual light emitting diode.
According to such a configuration, since an ultraviolet absorbent is mixed into a surface-layer portion of a resin encapsulator, a wavelength-converting material provided close to a light emitting diode element becomes insusceptible to externally-incoming ultraviolet radiation or the like and hence the aging of the wavelength-converting material can be controlled.
Since the ultraviolet absorbent is mixed into the surface-layer portion of the resin encapsulator alone, there is no fear of a substantial reduction in the brightness of a light emitting diode due to its mixing.
Even when a plurality of surface-mount type light emitting diodes are placed adjacent to each other since an upper surface of a first resin encapsulator charged in a reflection frame is placed in a position lower than an upper edge of the reflection frame, light emitting from one light emitting diode can be blocked by an upper edge of a reflection frame of the other light emitting diode, and luminescent colors of both the light emitting diodes are not mixed together.
Since a diffusing agent is mixed into a second resin encapsulator, wavelength-converted light is diffused to obtain a luminescent color having uniformity.
Since the second resin encapsulator is covered with a third resin encapsulator shaped in cap form over its entirety, the wavelength-converting material placed therein becomes more insusceptible to externally-incoming ultraviolet radiation or the like.
Since a condenser lens portion is formed on an upper surface of the third resin encapsulator, light emitted from a light emitting diode element is gathered by the condenser lens portion to obtain high-brightness luminescence.
According to a manufacturing method of the present invention, since a large number of surface-mount type light emitting diodes can simultaneously be fabricated on a glass epoxy assembled structure, great cost-down can be achieved and a large economical effect is obtained. Further, the condenser lens portion is formed integrally with a resin encapsulator and automatic mounting to a motherboard is allowed. In addition to these, a reduction in the number of man-days, an improvement in yield, and an improvement in reliability or the like can be achieved.